Exploring trimetallic clusters containing alkali and alkaline earth metal atoms with high activity for nitrogen activation

Abstract

Activation of dinitrogen (N2) is the critical step in nitrogen reduction reaction (NRR) in ammonia synthesis. In this paper, reaction mechanisms of N2 activation on trimetallic clusters Mo2M (M=Li, Na, K, Mg, and Ca) and Mo3-xCax (x = 2-3) were systematically studied by density functional theory calculations. Unlike Mo2 which is inert to N2 , clusters with alkali or alkaline earth metal atoms have much higher reactivity towards N2 in terms of both thermodynamics and kinetics. Particularly, in one reaction path of N2 with MoCa2 , all the intermediates and transition states are well below the energy sum of the reactants, indicating that the dissociation of N2 on MoCa2 can take place spontaneously in gas-phase reactions. N2 transfers on clusters with different coordination modes, and the N−N bond is gradually activated. When N2 is bonded with three metal atoms with end-on:side-on:side-on coordination mode, it is fully activated and easily dissociated into two adsorbed N atoms. These results may serve as a prototype to design single-cluster catalysts with a trimetallic center for nitrogen activation and conversion.

Trimetallic clusters in the sumanene bowl for dinitrogen activation

“…Mayer bond order (MBO) is a widely used physical quantity that could well describe the strength of covalent bonds. 44,54,64,89 The evolution of MBO of N-N bonds (MBO N-N ) in key intermediates and transition states is analyzed in Fig. 10.…”

“…The N-N bond length (R N-N ), Mayer bond order, 89 and vibration frequency (n N-N ) of the key intermediates and transition states were shown to compare the activation degree of N 2 during the reactions of N 2 with M 3 and C 21 H 12 -M 3 . MBO analysis is adopted since the MBO values of N 2 , N 2 H 2 , and N 2 H 4 are more in line with the chemical intuition, and our previous work on N 2 activation 54,64 has also proved that MBO analysis can well reflect the degree of nitrogen activation. All energies reported here include zero-point vibrational energy (ZPE) corrections unless otherwise specified.…”

“…[30][31][32] Therefore, using a cluster model to study the activation of nitrogen is an effective method. So far, the reaction of metal-containing clusters with N 2 has been widely studied, while only a few studies are based on trimetallic clusters, such as pure metals (Mo 2 M, where M = Li, Na, K, Mg, and Ca), 54 metal carbides (V 3 C 4 À , 55 V 3Àx Ta x C 4 À , 56 and FeV 2 C 2…”

Chemical Looping Ammonia Synthesis with High Performance Supported Molybdenum-based Nitrogen Carrier

“…钼基氨合成催化剂 [23][24][25][26][27] , 如过渡金属氮化物 Mo 2 N 因其良好的选择性及活性而被广泛应用于催化合成氨 领域 [28] . 由于 Mo 2 N 催化剂在固氮生成氨的过程中遵循 Mars-van Krevelen 机制 [29] , 该机制涉及氮空位的消耗及 补充, 这与化学链合成氨过程中的释氮及固氮过程有较 强的相似性.…”

Comparison of Nitrogen Activation on Trinuclear Niobium and Tungsten Sulfide Clusters Nb3Sn and W3Sn (n=0–3): A DFT Study

“…Currently, only a few studies involve the N 2 activation on clusters containing three active metals. [32][33][34][35][36] Thus, further studies are necessary to reveal the reaction mechanisms and the main factors affecting the reaction activity.…”